You have no constitutional right to access Facebook or Twitter
You DO have constitutional rights to access any private business if they are refusing you service based on discrimination(race, sex, age, religion, etc). However your right to free speech can be limited by a private business. The Supreme Court has specifically ruled on this in 2017 that you have a right to join Facebook UNLESS you intend to violate their terms of service.
However, Facebook can have their own "terms of service" which they can interpret however they want, thus making it possible to skirt around the discrimination laws and ban anyone they want. All of these issues are still being decided by the Supreme Court as social media is a relatively new phenomenon. But you have to be banned for your behavior or a violation of their terms of service, not any of the protected classes. Facebook could not say "no black people can join". There was a famous case where a cake maker was FORCED to make a wedding cake for a transgender wedding even though it was against his religious beliefs but he was fined for refusing service as now trans is a protected class exemption.
But facebook is operating on the internet, which has been determined to be public. Yet a website can be private. It is bringing up very interesting Constitutional questions that will be decided in the next 10 years. I'm not preaching anyone on here is right or wrong, as the Supreme Court and Constitutional lawyers are still trying to figure it out.
